In a typical web application, sections of web pages can be divided in multiple sections and some of these sections may be reusable across web pages. To reduce the duplication of similar markup/code, typically these sections are stored in separated files (e.g., fragments), then these fragments are included in the different pages using specialized markups (e.g. <include>). Typically, the fragments to be included on a page are predefined and the interactions between fragments are well known at application development time.
The classical approach to the use of fragments facilitates fragment reuse but has limitations in terms of the variety and nature of dynamic behavior that can be provided using prior approaches.